1. Field of the Invention
The present invention relates to an optically active novel compound and intermediate products thereof, and a process for the manufacture of same.
2. Description of the Related Art
Vitamin E is a methylated derivative of a tocopherol, and includes eight kinds of naturally occurring compounds, i.e., .alpha.-, .beta.-, .gamma.-, and .delta.-tocopherols, and .alpha.-, .beta.-, .gamma.-, and .delta.-tocotrienols. Although tocopherols and tocotrienols include d-form, l-form or dl-form optical isomers, naturally occurring compounds have optical activities. Synthesized tocopherols are generally prepared in the form of a diastereomer, and it is known that a chirality of the carbon atom of the 2-position in the chroman ring has a considerable affect on the physiological activities of tocopherols.
A method of synthesizing optically active tocopherols from optically active starting materials is described in, for example, N. Cohen, et al, Journal of the American Chemical Society, 101:22, Oct. 24, 1979, 6710-6716. In the method of Cohen, et al, an optically active desired .alpha.-tocopherol is obtained by using an optically active benzopyran derivative as a starting material, to form an optically active chroman-2-methanol derivative, and then performing a Wittig coupling of the chroman derivative to form the final .alpha.-tocopherol while retaining the chirality of the starting material. In this method, however, a resolution process is required to obtain the optically active starting material, and a poisonous hydrocyanic acid must be used during the course of the synthesis process.
Further, a method of synthesizing optically active tocopherols starting from optically active phytols is described in, for example, Japanese Unexamined Patent Publications No. 59-29678 and No. 59-31726. According to the methods described in said Publications, an epoxy group is stereo-selectively introduced into the 2, 3-position of the naturally occurring phytol by an enantioselective oxidation, and a reductive cleavage of the epoxy group is then performed to form a hydroxy group while retaining the chirality of the 3-position. After protecting the hydroxy group, the hydroxy group of the 1-position is oxidized to form an aldehyde group, and the obtained aldehyde group is reacted with a phenyl magnesium halide to introduce the benzene ring. A ring closure is then carried out, using the hydroxy group of the 3-position, and the desired chirality is introduced into the 2-position of the chroman ring.
In the above methods, however, many steps are required to selectively protect one of two hydroxy groups formed by the cleaving of the epoxy group. Further, because the .beta.-oxyaldehyde intermediate is unstable, it is difficult to determine the reaction conditions. Furthermore, other disadvantages arise in that Grignard reagent, which requires anhydrous condition, and ether must be used, and complicated steps for removing the hydroxy group in the benzyl position become necessary.
Mevalonolactone is a useful compound as a starting material of various medicines, agricultural chemicals, cosmetics or food additives, or the intermediates thereof, and includes an optically active R-form (naturally occurring) compound and S-form (naturally non-occurring) compound. The naturally occurring R-form compound has the structure of the formula (35): ##STR2##
A method of synthesizing optically active mevalonolactone from optically active starting materials is described in, for example, Japanese Unexamined Patent Publication No. 60-146840. In the method of this Patent Publication, an optically active heptenetriol derivative is prepared from an optically active oxohydroxyfuran derivative while retaining the chirality thereof, and the optically active desired mevalonolactone is then obtained through several steps from the heptenetriol derivative. In the conventional methods including the above, however, many steps are required, the chirality introducing rate is low, the procedures in the processes are difficult, and mass production is difficult.